The volatile political environment has led many programmatic buying platforms to shun Breitbart, but the Facebook Audience Network is still placing ads on the controversial publisher’s website.

One ad buyer recently discovered that FAN, which uses Facebook data to sell ads on apps and websites outside the social network, placed its client’s ads on Breitbart. The buyer knew it was through FAN because the creative was unique to the ad that ran through the network. The buyer then saw a screenshot taken by the ad activist account Sleeping Giants of this specific ad on Breitbart. After this snafu, the buyer said it’s advising its clients to avoid FAN altogether.

Facebook may not want to appear as if it’s censoring political opinion. But the ad buyer said FAN’s policies give advertisers the impression that websites like Breitbart aren’t included in the network. An email that a Facebook rep sent to the ad buyer states: “We verify that every publisher follows our Audience Network policies. This includes adherence to the Facebook Community Standards.” And FAN’s policies state that sites in the network must not discriminate against “personal attributes such as race, ethnicity, color, national origin, religion, age, sex, sexual orientation, gender identity, family status, disability, medical or genetic condition.”

Meanwhile, Breitbart headlines have claimed that women in tech “just suck at interviews,” female stars of the “Ghostbusters” reboot are “teenage boys with tits” and young Muslims in America are “a ticking time bomb.”

Other tech giants like Amazon and Google regularly serve ads on Breitbart, but those platforms provide more thorough reporting for ad buyers to check where their ads appear. The other qualm that this buyer had with FAN was that, without a list of the URLs where the campaign’s ads ran, the buyer couldn’t confirm its ads were on Breitbart until it started getting called out by activists.

While Facebook announced in June that it started testing out giving advertisers publisher placement lists, this ad-buying agency said those reports haven’t been made available to them yet. A Facebook spokesperson said the reports will be rolled out to advertisers within the next three weeks.

“[Facebook’s] black box ad net is touted as a way to use Facebook data to reach premium publishers off their platform, but they don’t release who those publishers are, and they refuse to give reports about where their ads run,” said the ad buyer said while requesting anonymity out of fear of getting on Facebook’s bad side. “Additionally, you have to trust Facebook’s categories without understanding at a URL level what domains might be included.”

A Facebook spokesperson said that advertisers on FAN can control what publishers their ads appear on because they have the option to block sites they don’t want to run on. The statement also read: “In addition, we will soon begin reviewing all publishers in the Audience Network on a placement by placement basis. If we find specific placements that are in violation of our policies, we will stop ads from running on those specific URLs.”

The video below shows a Breitbart banner ad being served by FAN. Above a headline that surrounds Trump adviser Gary Cohn’s name with globe emojis — the trope of calling Jews “globalists” or “cosmopolitan” dates back to Nazi Germany and “The Protocols of the Elders of Zion” — is an ad for fintech company CNote. Clicking on the ad brings up a page explaining that FAN served the ad. Breitbart did not reply to messages about this story.

Kieley Taylor, head of paid social at GroupM, said FAN’s placement of ads on Breitbart “just reinforces that we’ve made the right call in avoiding buying open web inventory via FAN.” Compared to other buying platforms, FAN lacks transparency and attribution reporting, she said. FAN also lacks an impression tracker to show exactly where ads run, said a rep from ad agency CTP Boston.

David Lee, programmatic lead at ad agency The Richards Group, said that given all the hubbub over ads on YouTube appearing against extremist content, continuing to limit reporting while placing ads on a controversial site like Breitbart gives ad buyers the impression that Facebook “didn’t learn anything from the recent brand-safety issues.”